Fuel Pump???

[whitekysho]

I am getting a bucking at all engine speeds, I have replaced the DIS, cleaned the MAF and IAT sensor, and unplugged the CPS. When I prime the pump the fuel pressure starts at 0 psi and takes 3-4 cycles to get to 30psi and stays steady at 30psi when running. Do you all think it is the fuel pump?

BTW I have a 1991 MTX.

Thanks in advance.

 

[SHOlover1]

did you check the codes sounds like the cid but fuel pressure should stay consant or so i thought

 

[whitekysho]

Is it possible for my 91 to throw 3 digit codes?

 

[SASHO91]

Have you changed the fuel filter yet?? And if the EEC has been swapped for a later model then yes, it can produce 3 digit codes. Check which EEC you have.

 

[whitekysho]

I changed the fuel filter about 30,000 miles ago. Wouldn't my EEC have to be an early one since I don't have EGR?

 

[whitekysho]

It was not the fuel pump, I guess next is the CID...

 

[SASHO91]

How did you confirm that it wasn't the pump.

 

[Mr Anonymous]

How did you confirm that it wasn't the pump.

I would have the same question.

For starters, with the vacuum line to the FPR disconnected from the manifold (and the ****** on the manifold plugged), you should see 39PSI with the engine running.

Also, upon priming by turning the key to run, you should see the fuel pressure immediately shoot to ~35PSI and stay there.

 

[shobote]

Do you have an oiled cone filter ? If so, it only takes a very short time for the oil on those things to re-contaminate the MAF filament. If this cone filter is not sealed under the hood, you are also losing hp versus the stock airbox which is a CAI; I would clean the MAF filament and then put the stock airfilter assembly back on.

 

[whitekysho]

I figured it out by replacing it. I have also cleaned the MAF.

 

[93rev2sev]

Have you UNPLUGGED the MAF and drove around for a while?

 

[whitekysho]

Yes I have, I am replacing the CDI right now.

 

[whitekysho]

The CID did not fix it, what next? Junkyard MAF? I received a 66 code.